author | wenzelm |
Fri, 15 Dec 2000 17:59:30 +0100 | |
changeset 10680 | 26e4aecf3207 |
parent 9930 | c02d48a47ed1 |
child 11046 | b5f5942781a0 |
permissions | -rw-r--r-- |
3424 | 1 |
(* Title: HOL/Induct/Mutil |
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ID: $Id$ |
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Author: Lawrence C Paulson, Cambridge University Computer Laboratory |
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Copyright 1996 University of Cambridge |
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The Mutilated Chess Board Problem, formalized inductively |
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Originator is Max Black, according to J A Robinson. |
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Popularized as the Mutilated Checkerboard Problem by J McCarthy |
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*) |
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Mutil = Main + |
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consts tiling :: "'a set set => 'a set set" |
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inductive "tiling A" |
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intrs |
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empty "{} : tiling A" |
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Un "[| a: A; t: tiling A; a Int t = {} |] ==> a Un t : tiling A" |
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consts domino :: "(nat*nat)set set" |
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inductive domino |
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intrs |
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horiz "{(i, j), (i, Suc j)} : domino" |
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vertl "{(i, j), (Suc i, j)} : domino" |
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constdefs |
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coloured :: "nat => (nat*nat)set" |
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"coloured b == {(i,j). (i+j) mod #2 = b}" |
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end |